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Kernel: Add a more expressive API for getting random bytes

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We now have these API's in <Kernel/Random.h>:

    - get_fast_random_bytes(u8* buffer, size_t buffer_size)
    - get_good_random_bytes(u8* buffer, size_t buffer_size)
    - get_fast_random<T>()
    - get_good_random<T>()

Internally they both use x86 RDRAND if available, otherwise they fall
back to the same LCG we had in RandomDevice all along.

The main purpose of this patch is to give kernel code a way to better
express its needs for random data.

Randomness is something that will require a lot more work, but this is
hopefully a step in the right direction.
This commit is contained in:
Andreas Kling 2020-01-03 12:36:30 +01:00
parent 24cc67d199
commit 9026598999
11 changed files with 87 additions and 48 deletions
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29
Kernel/Devices/RandomDevice.cpp
View file

@ -1,5 +1,5 @@
#include "RandomDevice.h"
#include <AK/StdLibExtras.h>
#include <Kernel/Devices/RandomDevice.h>
#include <Kernel/Random.h>
RandomDevice::RandomDevice()
: CharacterDevice(1, 8)
@ -10,22 +10,6 @@ RandomDevice::~RandomDevice()
{
}
static u32 next = 1;
#define MY_RAND_MAX 4294967295U
u32 RandomDevice::random_value()
{
next = next * 1103515245 + 12345;
return next;
}
#if 0
static void mysrand(unsigned seed)
{
next = seed;
}
#endif
bool RandomDevice::can_read(const FileDescription&) const
{
return true;
@ -33,13 +17,8 @@ bool RandomDevice::can_read(const FileDescription&) const
ssize_t RandomDevice::read(FileDescription&, u8* buffer, ssize_t size)
{
const int range = 'z' - 'a';
ssize_t nread = min(size, PAGE_SIZE);
for (ssize_t i = 0; i < nread; ++i) {
u32 r = random_value() % range;
buffer[i] = (u8)('a' + r);
}
return nread;
get_good_random_bytes(buffer, size);
return size;
}
ssize_t RandomDevice::write(FileDescription&, const u8*, ssize_t size)